[RFI] rfi to computer via sound card

Jon Ogden Jon.Ogden@cain-forlaw.com
Thu, 30 May 2002 15:59:41 -0500


There may be other unknown factors in this.  I discovered with my PC and
sound card a problem.  I had a cable running from my modem to my sound
card internally in the PC.  I disconnected it and the RFI went away.
Also, there's the cable that usually runs from the CD-Rom to the sound
card as well.  You might want to try putting a ferrite on that too.

It may be the cable on the input but it may be something else connected
internally to the sound card.

Good luck!



Jon Ogden
Sales Engineer
Cain-Forlaw Company
847-202-9898 (Voice)
847-202-9896 (Fax)

> -----Original Message-----
> From: Pete Smith [mailto:n4zr@contesting.com]
> Sent: Thursday, May 30, 2002 3:40 PM
> To: rfi@contesting.com
> Subject: [RFI] rfi to computer via sound card
> I'm setting up to record contests using an SB-16 sound card 
> and Recall Pro 
> software.  At the moment I'm dealing with a severe RFI problem, which 
> crashes the Recall software a few seconds into every 
> transmission.  I've 
> determined that it is definitely coming in the [line in] 
> cable from my 
> radio's external AF output, because when I disconnect that 
> line from the 
> computer the program doesn't crash no matter how long I 
> transmit.  I've 
> grounded the computer case and wound a number of turns of the 
> [line in] 
> cable around ferrite toroid cores, all without apparent 
> benefit.  Would it 
> make sense to try .01 disc caps bypassing the conductors in 
> the [line in] 
> cable to the shield, in case this is differential mode 
> interference rather 
> than common mode, as I'd assumed?
> 73, Pete N4ZR
> Check out the World HF
> Contest Station Database at
> www.pvrc.org
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